The present invention pertains to a graphics printer roller transport apparatus and method for transporting workpieces through a multi-pass graphics printer apparatus.
Currently, graphics printers are used to print images onto a work item such as plastic cards. One frequently used application is to create photo identification (ID) cards bearing an image of the card holder. Card holder images are captured by use of such apparatus as video cameras or scanners. Once the card holder images are digitized they are typically displayed on a display monitor where the image is edited; e.g., sized and cropped, for use on the ID card. Once the images are suitably adjusted for use on the ID card, they are electronically stored for subsequent printing onto an ID card using a graphics printer apparatus.
There are various graphics printing apparatus and methods for printing images onto workpieces such as ID cars. The existing systems are usually rather expensive and complicated. In addition, many systems do not provide the desired resolution. A typical method for printing a color image on a workpiece is to use a color ribbon having three different primary color panels; yellow, magenta, and cyan. To create a color image, the printer apparatus sequentially prints each of the three primary colors onto the workpiece to create a composite color image. This is typically referred to as multipass printing. Multipass printing requires that the printer apparatus be accurately positioned relative to the workpiece for the printing of each primary color. Unless the printer apparatus and workpiece are properly positioned unwanted blurring will occur due to misalignment of the three primary colors in the color image.
In an effort to provide the desired image clarity, existing printer apparatus are often expensive and complex in their structure. One of the most expensive and complex aspects of these printer apparatus is the transport mechanism used to transport the workpiece past the print head and then reposition the workpiece and/or print head for subsequent passes during the multipass printing process.
Single pass printers have used roller transport systems to transport the workpiece past the printer. However, these roller transport systems are typically deemed inaccurate for multipass printing. Typically roller transport systems use a sensor to locate either the leading or trailing edge of the workpiece. The workpiece is typically moved under the print head at a rate equal to the print resolution by a stepper motor rotating one motor step per print line. Gears and/or belts are used to produce an acceptable ratio so that a single motor step movement equals a print line. The maximum sensing error in such a system is a single motor step or one print line. For multipass printing, this is usually considered an unacceptable error.
The present invention provides a low cost graphics printer apparatus using a roller transport system which provides desired image quality. In addition, various embodiments of the present invention solves many other problems associated with existing graphics printers.